High performance spiral-wound catheter

ABSTRACT

This invention is a surgical device. In particular, it is a catheter suitable for accessing a tissue target within the body, typically a target which is accessible through the vascular system. Central to the invention is the use of a stiffener ribbon, typically metallic, wound within the catheter body in such a way as to create a catheter having controllable stiffness. The stiffener ribbon is adhesively bonded to a flexible outer tubing member so to produce a thin wall catheter section which is exceptionally flexible but highly kink resistant. The catheter sections made according to this invention may be used in conjunction with other catheter sections either using the concepts shown herein or made in other ways. Because of the effective strength and ability to retain a generally kink-free form, these catheters may be effectively used in sizes which are quite fine, e.g., 0.015&#34; to 0.020&#34; in diameter, and useable within typical vascular catheters.

This application is a division of application Ser. No. 08/338,018 filedNov. 10, 1994, now pending.

FIELD OF THE INVENTION

This invention is a surgical device. In particular, it is a cathetersuitable for accessing a tissue target within the body, typically atarget which is accessible through the vascular system. Central to theinvention is the use of a stiffener ribbon, typically metallic, woundwithin the catheter body in such a way to create a catheter having anexceptionally thin wall and controlled stiffness. The stiffener ribbonis adhesively bonded to a flexible outer tubing member so to produce acatheter section which is very flexible but highly kink resistant.

The catheter sections made according to this invention may be used inconjunction with other catheter sections either using the concepts shownherein or made in other ways. Because of the effective strength andability to retain a generally kink-free form, these catheters may beeffectively used in sizes which are quite fine, e.g., 0.015" to 0.020"in diameter, and usable within typical vascular catheters.

BACKGROUND OF THE INVENTION

Catheters are increasingly used to access remote regions of the humanbody and, in doing so, delivering diagnostic or therapeutic agents tothose sites. In particular, catheters which use the circulatory systemas the pathway to these treatment sites are especially practical.Catheters are also used to access other regions of the body, e.g.,genito-urinary regions, for a variety of therapeutic and diagnosticreasons. One such treatment of diseases of the circulatory system is viaangioplasty (PCTA). Such a procedure uses catheters having balloons ontheir distal tips. It is similarly common that those catheters are usedto deliver a radiopaque agent to the site in question prior to the PCTAprocedure to view the problem prior to treatment.

Often the target which one desires to access by catheter is within asoft tissue such as the liver or the brain. These are difficult sites toreach. The catheter must be introduced through a large artery such asthose found in the groin or in the neck and then be passed throughever-narrower regions of the arterial system until the catheter reachesthe selected site. Often such pathways will wind back upon themselves ina multi-looped path. These catheters are difficult to design and toutilize in that they must be fairly stiff at their proximal end so toallow the pushing and manipulation of the catheter as it progressesthrough the body, and yet must be sufficiently flexible at the distalend to allow passage of the catheter tip through the loops andincreasingly smaller blood vessels mentioned above and yet at the sametime not cause significant trauma to the blood vessel or to thesurrounding tissue. Further details on the problems and an early, butyet effective, way of designing a catheter for such a traversal may befound in U.S. Pat. No. 4,739,768, to Engelson. These catheters aredesigned to be used with a guidewire. A guidewire is simply a wire,typically of very sophisticated design, which is the "scout" for thecatheter. The catheter fits over and slides along the guidewire as itpasses through the vasculature. Said another way, the guidewire is usedto select the proper path through the vasculature with the urging of theattending physician and the catheter slides along behind once the properpath is established.

There are other ways of causing a catheter to proceed through the humanvasculature to a selected site, but a guidewire-aided catheter isconsidered to be both quite quick and somewhat more accurate than theother procedures. One such alternative procedure is the use of aflow-directed catheter. These devices often have a small balloonsituated on the distal end of the catheter which may be alternatelydeflated and inflated as the need to select a route for the catheter isencountered.

This invention is an adaptable one and may be used in a variety ofcatheter formats. The invention utilizes the concept of adhesivelycombining one or more polymeric tubes with one or more spirally woundribbons (each wound in the same direction) to control the stiffness ofthe resultant catheter section or body. The construction techniqueallows the production of catheter sections having very smalldiameters--diameters so small that the secondary catheters may be usedinterior to other vascular catheters, with or without guidewires. Thiscatheter may be used in conjunction with a guidewire, but the catheterbody may also be used as a flow-directed catheter with the attachment ofa balloon or in combination with a specifically flexible tip, as isseen, for instance, in U.S. Pat. No. 5,336,205 to Zenzen et al., theentirety of which is incorporated by reference.

The use of ribbons in winding a catheter body is not a novel concept.Typical background patents are discussed below. However, none of thesedocuments have used my concept to produce a catheter which has thephysical capabilities of the catheter of this invention.

Multi-Wrap Catheters

There are a number of catheters discussed in the literature whichutilize catheter bodies having multiply wrapped reinforcing material.These catheters include structures having braided bands or ones in whichthe spirally wound material is simply wound in one direction and thefollowing layer or layers are wound in the other.

Crippendorf, U.S. Pat. No. 2,437,542, describes a "catheter-typeinstrument" which is typically used as a ureteral or urethral catheter.The physical design is said to be one having a distal section of greaterflexibility and a proximal section of lesser flexibility. The device ismade of intertwined threads of silk, cotton, or some synthetic fiber. Itis made by impregnating a fabric-based tube with a stiffening mediumwhich renders the tube stiff yet flexible. The thus-plasticized tubingis then dipped in some other medium to allow the formation of a flexiblevarnish-like layer. This latter material may be a tung oil base or aphenolic resin and a suitable plasticizer. There is no indication thatthis device is of the flexibility described herein. Additionally, itappears to be the type which is used in some region other than in thebody's periphery or in its soft tissues.

Similarly, U.S. Pat. No. 3,416,531, to Edwards, shows a catheter havingbraiding-edge walls. The device further has additional layers of otherpolymers such as TEFLON and the like. The strands found in the braidingin the walls appear to be threads having circular cross-sections. Thereis no suggestion of constructing a device using ribbon materials.Furthermore, the device is shown to be fairly stiff in that it isdesigned so that it may be bent using a fairly large handle at itsproximal end.

U.S. Pat. No. 3,924,632, to Cook, shows a catheter body utilizingfiberglass bands wrapped spirally for the length of the catheter. As isshown in FIG. 2 and the explanation of the FIG. at column 3, lines 12and following, the catheter uses fiberglass bands which are braided,that is to say, bands which are spiralled in one direction cross overand under bands which are spiraled in the opposite direction.Additionally, it should be observed that FIG. 3 depicts a catheter shafthaving both an inner lining or core 30 and an outer tube 35.

U.S. Pat. No. 4,425,919, to Alston, Jr. et al., shows a multilayeredcatheter assembly using multi-stranded flat wire braid. The braid 14 inFIG. 3 further covers an interior tubing or substrate 12.

U.S. Pat. No. 4,484,586 shows a method for the production of a hollow,conductive medical tubing. The conductive wires are placed in the wallsof hollow tubing specifically for implantation in the human body,particularly for pacemaker leads. The tubing is preferably made of anannealed copper wire which has been coated with a body-compatiblepolymer such as a polyurethane or a silicone. After coating, the copperwire is wound into a tube. The wound substrate is then coated with stillanother polymer to produce a tubing having spiral conducting wires inits wall.

A document showing the use of a helically wound ribbon of flexiblematerial in a catheter is U.S. Pat. No. 4,516,972, to Samson. Thisdevice is a guiding catheter and it may be produced from one or morewound ribbons. The preferred ribbon is an aramid material known asKevlar 49. Again, this device is a device which must be fairly stiff. Itis a device which is designed to take a "set" and remain in a particularconfiguration as another catheter is passed through it. It must be softenough so as not to cause substantial trauma, but it is certainly notfor use with a guidewire. It would not meet the flexibility criteriarequired of the inventive catheter described herein.

U.S. Pat. No. 4,806,182, to Rydell et al, shows a device using astainless steel braid imbedded in its wall and having an inner layer ofa polyfluorocarbon. The process also described therein is a way tolaminate the polyfluorocarbon to a polyurethane inner layer so as toprevent delamination.

U.S. Pat. No. 4,832,681, to Lenck, shows a method and apparatus usefulfor artificial fertilization. The device itself is a long portion oftubing which, depending upon its specific materials of construction, maybe made somewhat stiffer by the addition of a spiral reinforcementcomprising stainless steel wire.

U.S. Pat. No. 4,981,478, to Evard et al., discloses a multi-sectioned orcomposite vascular catheter. The interior section of the catheterappears to have three sections making up the shaft. The most interior(and distal) section, 47, appears to be a pair of coils 13 and 24 havinga polymeric tubing member 21 placed within it. The next, more proximal,section is 41, and FIG. 4 shows it to be "wrapped or braided" about thenext inner layer discussed just above. The drawing does not show it tobe braided but, instead, a series of spirally wrapped individualstrands. Finally, the outermost tubular section of this catheter core isanother fiber layer 49, of similar construction to the middle section 26discussed just above. No suggestion is made that any of these multiplelayers be simplified into a single, spirally-wrapped layer adhesivelybound to an outer polymeric covering.

Another catheter showing the use of braided wire is shown in U.S. Pat.No. 5,037,404, to Gold et al. Mention is made in Gold et al of theconcept of varying the pitch angle between wound strands so to result ina device having differing flexibilities at differing portions of thedevice. The differing flexibilities are caused by the difference inpitch angle. No mention is made of the use of ribbon, nor is anyspecific mention made of the particular uses to which the Gold et al.device may be placed.

U.S. Pat. No. 5,057,092, to Webster, Jr., shows a catheter device usedto monitor cardiovascular electrical activity or to electricallystimulate the heart. The catheter uses braided helical members having ahigh modulus of elasticity, e.g., stainless steel. The braid is a fairlycomplicated, multi-component pattern shown very well in FIG. 2.

U.S. Pat. No. 5,176,660 shows the production of catheters havingreinforcing strands in their sheath wall. The metallic strands are woundthroughout the tubular sheath in a helical crossing pattern so toproduce a substantially stronger sheath. The reinforcing filaments areused to increase the longitudinal stiffness of the catheter for good"pushability". The device appears to be quite strong and is wound at atension of about 250,000 lb./in.² or more. The flat strands themselvesare said to have a width of between 0.006 and 0.020 inches and athickness of 0.0015 and 0.004 inches. There is no suggestion to usethese concepts in devices having the flexibility and otherconfigurations described below.

Another variation which utilizes a catheter wall having helically placedliquid crystal fibrils is found in U.S. Pat. No. 5,248,305, to Zdrahala.The catheter body is extruded through an annular die, having relativelyrotating inner and outer mandrel dies. In this way, the tube containingthe liquid crystal polymer plastic-containing material exhibits a bit ofcircumferential orientation due to the rotating die parts. At column 2,line 40 and following, the patent suggests that the rotation rate of theinner and outer walls of the die may be varied as the tube is extruded,with the result that various sections of the extruded tube exhibitdiffering stiffnesses.

U.S. Pat. No. 5,217,482 shows a balloon catheter having a stainlesssteel hypotube catheter shaft and a distal balloon. Certain sections ofthe device shown in the patent use a spiral ribbon of stainless steelsecured to the outer sleeve by a suitable adhesive to act as atransition section from a section of very high stiffness to a section ofcomparatively low stiffness.

Japanese Kokai 05-220,225, owned by the Terumo Corporation, describes acatheter in which the torsional rigidity of the main body is varied byincorporating onto an inner tubular section 33, a wire layer which istightly knitted at the proximal section of the catheter and more looselyknitted at a midsection.

Single-Layer. Reinforced Catheters

There are a variety of catheters which, unlike the devices discussedabove, utilize but a single layer of reinforcing material.

For instance, U.S. Pat. No. 243,396 to Pfarre, patented in June of 1881,shows the use of a surgical tube having a wire helix situated within thetube wall. The wire helix is said to be vulcanized into the cover of thedevice.

U.S. Pat. No. 2,211,975, to Hendrickson, shows a similar device alsocomprising a stainless steel wire 15 embedded in the inner wall of arubber catheter.

U.S. Pat. No. 3,757,768, to de Toledo, shows a "unitary, combined springguide-catheter that includes an inner wall portion formed as acontinuous helical spring with the helices in contact with each otherand an outer wall portion formed from an inert plastic materialenclosing the spring in such a manner as to become firmly bonded to thespring while having its outer surface smooth". There is no suggestion toseparate the windings of the coil in any fashion.

U.S. Pat. No. 4,430,083 describes a catheter used for percutaneousadministration of a thrombolytic agent directly to a clot in a coronaryartery. The device itself is an elongated, flexible tube supported byhelically wound wire having a specific cross-sectional shape. The wireis wound into a series of tight, contiguous coils to allow heatshrinking of tubing onto the outside of the wire of the shape of theouter surface of the wire as wound into the helix-provides theheat-shrunk tubing with footing for a tight fit.

U.S. Pat. No. 4,567,024, to Coneys, shows a catheter which employs a setof helical strips within the wall of the catheter. However, the helicalstrips are of a radiopaque material, e.g., fluorinatedethylenepropylene. It is not clear that the blended radiopaque materialnecessarily provides any physical benefit other than the ability toallow the catheter shaft to be seen when viewed with a fluoroscope.

U.S. Pat. No. 4,737,153, to Shimamura et al., describes a device whichis characterized as a "reinforced therapeutic tube" and which uses aspiral reinforcing material embedded within the wall of the device.

U.S. Pat. No. 5,069,674, to Fearnot et al. (and its parent, U.S. Pat.No. 4,985,022), shows a small diameter epidural catheter having a distaltip made up of a stainless steel wire which is helically wound andplaced within a tubular sheath or tube. There is no suggestion withinthe patent that the interior coil be made to adhere to the outer tubularsheath.

Similarly, U.S. Pat. No. 5,178,158, to de Toledo, shows what ischaracterized as a "convertible wire for use as a guidewire orcatheter". The patent describes a structure which comprises an interiorwire or spring section shown, in the drawings, to be of generallyrectangular cross-section. Outer layers of the device include apolyamide sheath placed adjacent to the helical coil at the proximal endof the catheter (see column 4, lines 64 and following). The device alsocomprises an outer sheath 40 of Teflon that extends from the proximalend 12 to the distal end 14 of the device. The overlying sheath 40 mayextend or overhang at the proximal or the distal end of the catheter.The distal tip portion 13 is said to be "flexible, soft, and floppy".There is no suggestion of utilizing an adhesive to bond the interiorwire to the exterior tubing. The PCT Published Application correspondingto this patent is WO 92/07507.

U.S. Pat. 5,184,627 shows a guidewire suitable for infusion ofmedicaments to various sites along the guidewire. The guidewire is madeup of a helically wound coil having a polyamide sheath enclosing itsproximal portion and a Teflon sheath tightly covering the entire wirecoil. The coil is closed at its distal end. There is no suggestion thatthe wire forming the helical core be adhesively attached to its outercoverings.

U.S. Pat. No. 5,313,967, to Lieber et al., shows a medical device aportion of which is a helical coil which, apparently, may include anouter plastic sheath in some variations. Apparently, a secondary helixof a somewhat similar design, in that it is formed by rotating a flatwire or the like along its longitudinal axis to form a screw-likeconfiguration, is included within the helical coil to provide axialpushability and torque transmission.

The PCT application, WO 93/15785, to Sutton et al., describeskink-resistant tubing made up of a thin layer of an encapsulatingmaterial and a reinforcing coil. As is shown in the drawings, thesupporting material is embedded within the wall of the tubing in eachinstance.

The PCT application bearing the number WO 93/05842, to Shin et al.,shows a ribbon-wrapped catheter. The device is shown as a section of adilatation catheter. The inner section 34 is a helically wound coil andis preferably a flat wire. See, page 6, lines 25 and following. The coilis then wrapped with a heat-shrunk jacket 34 formed of low-densitypolyethylene. A lubricious material such as a silicone coating may thenbe placed on the inner surface of the spring coil to "enhance handlingof the guidewire". It is also said, on page 6 of the document, that the"entire spring coil, before it is wound or jacketed, may be coated withother materials such as Teflon to enhance lubricity or provide otheradvantages. In some embodiments, the spring coil has been plated withgold." The document does not suggest that the coil be made to adhere tothe outer polymeric jacket using an adhesive.

Endoscope Structures

Various endoscopic structures, used primarily in sizes which are largerthan endovascular catheters utilize structures including stiffenermaterials.

U.S. Pat. No. 4,676,229, to Krasnicki et al., describes an endoscopicstructure 30 having an ultrathin walled tubular substrate 31 formed of alubricious material such as TEFLON. The structure contains a filamentsupported substrate. The filament is coated with and embedded into afiller material, typically an elastomeric material. A highly lubriciousouter coating 35, all as shown in FIG. 2, forms the outer layer of thedevice. FIG. 3 in Krasnicki et al., describes another variation of theendoscopic device in which a different selection of polymer tubing isutilized but the placement of the filamentary support remains varied inan intermediate material of an elastomer. In some variations of thedevice, the filament is strongly bonded to the inner tubular substrateusing an adhesive 37 "such as an epoxy cement having sufficient bondstrength to hold the filament to the substrate as it is deformed into atight radius." See, column 3, lines 50 and following.

U.S. Pat. No. 4,899,787, to Ouchi et al. (and its foreign relative,German Offenlegungshrifft DE-3242449) describes a flexible tube for usein an endoscope having a flexible, basic tubular core structure made upof three parts. The three parts are an outer meshwork tube, anintermediate thermoplastic resin tube bonded to the outer meshwork tube,and an inner ribbon made of a stainless steel or the like which isadherent to the two polymeric and meshwork tubes such that the resintube maintains an adherent compressive pressure in the finished flexibletube. The patent also suggests the production of an endoscope tubehaving "flexibility which varies in step-wise manner from one end of thetube to the other . . . and is produced! by integrally bonding two ormore thermoplastic resin tube sections formed of respective resinmaterials having different hardnesses to outer surface of the tubularcore structure . . .". See, column 2, lines 48 and following.

U.S. Pat. No. 5,180,376 describes an introducer sheath utilizing a thin,flat wire metal coil surrounded only on its exterior surface with aplastic tube of coating. The flat wire coil is placed there to lower the"resistance of the sheath to buckling while minimizing the wallthickness of the sheath." A variation using two counter-wound metalribbons is also described. No suggestion of the use of an adhesive ismade in the patent.

European Patent Application 0,098,100 describes a flexible tube for anendoscope which uses a helically wound metallic strip having a braidedcovering contiguous to the outer surface of the coil and having stillfurther out a polymeric coating 9. Interior to the coil is a pair ofslender flexible sheaths which are secured to a "front-end piece 10" bysoldering.

Japanese Kokai 2-283,346, describes a flexible endoscope tube. Thetubular outer shell is made up of two layers of a high molecular weightlaminated material. The tube also has an inner layer of an elasticmaterial and interior to it all is a metallic ribbon providingstiffening.

Japanese Kokai 03-023830, also shows the skin for flexible tube used inan endoscope which is made up of a braid 3 prepared by knitting a finewire of a metal with a flexible portion 2 which is prepared by spirallywinding an elastic belt sheet-like material and a skin 4 with which thewhole outer surface of the device is covered. The document appears toemphasize the use of a particular polyester elastomer.

Japanese Kokai 5-56,910, appears to show a multi-layered endoscope tubemade up of layers of the spiral wound metallic ribbon covered by apolymeric sheath.

French Patent Document 2,613,231, describes a medical probe used with anendoscope or for some other device used to stimulate the heart. Thedevice appears to be a helix having a spacing between 0 and 0.25 mm (Seepage 4, line 20) preferably rectangular in cross section (See Page 4,Line 1) and of a multi-phase alloy such as M35N, SYNTACOBEN, or ELGELOY(See Page 4).

German Offenlegungshrifft DE-3642107 describes an endoscope tube, formedof a spiral tube, a braid formed of fibers interwoven into a net (whichbraid is fitted on the outer peripheral surface of the spiral tube), anda sheath covering the outer peripheral surface of the braid.

None of the noted devices have the structure required by the claimsrecited herein.

Other Anti-kinking Configurations

U.S. Pat. No. 5,222,949, to Kaldany, describes a tube in which anumber-of circumferential bands are placed at regular intervals along acatheter shaft. The bands may be integrated into the wall of thecatheter. A variety of methods for producing the bands in the tubularwall are discussed. These methods include periodically irradiating thewall to produce bands of a higher integral of cross-linking.

European Patent Application No. 0,421,650-A1 describes a method forproducing a catheter from a roll of polymer film while incorporatingother materials such as tinfoil elements or the like.

None of the documents cited above provides a structure required by thedisclosure and claims recited below, particularly when the flexibilityand ability to resist kinks is factored into the physical description ofthe devices.

SUMMARY OF THE INVENTION

This invention is a catheter section made up of one or more spirallywound stiffener ribbons adhesively attached to an outer polymericcovering.

The stiffener ribbon is, in its most basic form, a single strand ofribbon wound in a single direction. A number of ribbons of the same ordiffering sizes and compositions may also be used, but such ribbons arewound the same direction to form a single layer of ribbon and form alumen from the distal to the proximal end of the catheter section. Theribbons are typically metallic but may be of other materials. I havefound that a necessary portion of the invention is the requirement thatthe ribbons adhere to the outer covering. In this way, the kinkresistance of the catheter section is established due to the lack ofslippage between the cover and the spiral coil. The outer cover, in theregions between coil turns, retains a high level of patency. The absenceof slippage prevents the formation of localized areas of larger spacingbetween coil turns and the resulting source of kinking sites.

The catheter sections of this invention may be formed into an integralcatheter assembly. Wise choices of materials permit the catheter to beof a smaller overall diameter with a superior critical diameter. Indeed,one variation of this invention involves telescoping catheters with aninner catheter of this construction, perhaps with an inner guidewire.The catheter may be designed to integrate lubricious materials into thebase design of a particular catheter product without adding extraneousthickness and stiffness The catheter may be wholly constructed ofmaterials which are stable to radioactive sterilization procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in side view, a typical three section catheter.

FIG. 2 shows, in magnification, a section of the inner portion of oneinventive section of this catheter.

FIG. 3 shows, in magnification and cross-section, a variation of theinvention using two ribbons.

FIG. 4 shows, in magnified fractional view, a multisection catheterassembly.

FIGS. 5-8 show, in magnified cross-section, various catheters havingsections of differing stiffness.

FIG. 9 shows, in cross-section, a combination of outer and innercatheter sections made according to the invention and an innerguidewire, all in slidable relationship to each other.

FIGS. 10A and 10B show details of methods for determining the "criticalbend diameter" for a catheter.

DESCRIPTION OF THE INVENTION

This invention is a kink-resistant catheter section or a catheter. If acatheter, it is a composite device having at least one section includingat least one helically wound ribbon stiffener coaxial to and adhesivelyattached to at least one polymeric outer section. The ribbon forms theinner lumen of the catheter section. The catheter is configured so thatat least the distal portion of the catheter has a critical bend diameterof no more than 3.5 mm, preferably no more than 2.5 mm, more preferablyno more than 1.5 mm, and most preferably no more than 1.0 mm. I haveadditionally found that the radial compression strength of the sectionis quite high as compared to distal sections found on comparablecatheters.

A typical multi-section catheter (100) which may incorporate theconcepts of this invention is shown in FIG. 1. Such a catheter isdescribed in more detail in U.S. Pat. No. 4,739,768, to Engelson, (theentirety of which is incorporated by reference) and is particularlysuitable for neurological and peripheral vascular applications. Clearly,then, it is also suitable for less demanding service such as might beencountered in access and treatment of the heart. One difficulty whichhas arisen as higher demands for length have been placed on thesecatheters is that the diameter of the distal section necessarily becomessmaller and smaller. This is so since the longer catheters must reachever more smaller vascular areas. This smaller diameter requires aconcomitant thinning of the wall section. The thinner section walls maykink or ripple when actively pushed along the guidewire or whenvasoocclusive devices are pushed through the catheter's lumen. Thetypical configuration shown in FIG. 1 has a distal section (102) havingsignificant flexibility, an intermediate section (104) which istypically less flexible, and a long proximal section (106) which in turnis least flexible. The distal section (102) is flexible and soft toallow deep penetration of the extraordinary convolutions of theneurological vasculature without trauma. Various known and oftennecessary accessories to the catheter assembly, e.g., one or moreradiopaque bands (108) at the distal region to allow viewing of theposition of the distal region under fluoroscopy and a luer assembly(110) for guidewire (112) and fluids access are also shown in FIG. 1.The typical dimensions of this catheter are:

Overall length: 60-200 cm

Proximal Section (106): 60-150 cm

Intermediate Section (104): 20-50 cm

Distal Section (102): 2.5-30 cm

Obviously, these dimensions are not particularly critical to thisinvention and are selected as a function of the malady treated and itssite within the body. However, as will be discussed below, use of thespiral wound ribbon permits the walls of the catheter to be somewhatthinner with no diminution of performance, e.g., crush strength orflexibility, and, indeed, usually provides an improvement inperformance.

FIG. 2 shows a magnified cross-section of a catheter body or section(200) showing the most basic aspects of one variation of the invention.As shown there, the catheter body or section has a helically woundribbon (202) and an adhesive (204) on at least an outer portion of theribbon (202). Typically, the outer tubing member (206) is polymeric.Preferably, the outer tubing member (206) is'produced of a polymer whichis heat shrinkable onto the adhesive (204). Such polymers include knownmaterials such as polyethylene, polyvinylchloride (PVC),ethylvinylacetate (EVA), polyethylene terephalate (PET), and theirmixtures and copolymers. One very useful class of polymers are thethermoplastic elastomers, particularly polyesters. Typical of this classis HYTREL. Similarly, the adhesive (204) is desirably a thermoplasticwhich may be coated onto the inner lumen of the outer tubing member(206), the outer surface of the coil (as wound), the ribbon itself, ormay be formed in situ by the use of a mixture of polymers such aspolyethylene and EVA, which when heated to a proper temperature exudethe EVA onto the ribbon. A very highly desirable combination--from anassembly point of view--is the use of an thermoplastic adhesive (204)having a softening temperature between the temperature for heatshrinking the outer tubing (206) onto the adhesive (204) and the meltingtemperature of that outer tubing (206).

I have found that an outer covering of EVA having a suitablesoftening/heat shrinking temperature is an excellent choice for securinga strong bond to the ribbon particularly with an adhesive such aspolyester or polyimide. The EVA (obviously, with or without other mixedpolymers and fillers) is typically extruded into a taking of anappropriate size and thickness and cross-linked to raise the melttemperature of the resultant tubing. The tubing is then inflated and,perhaps, stretched to give the included polymer molecular orientation.The tubing may then be heat-shrunk onto the catheter. A suitable EVAwould have significant adhesive properties at about 300° F.

This is not to exclude the use of other polymers, depending on thesection of the catheter in which the section is used. For instance, thetubing may be of any of a variety of polymers, variously stiff orflexible. For instance, if the section (200) is used as a proximalsection, the outer tubing member (206) may be a polyimide, polyamidessuch as the Nylons, high density polyethylene (HDPE), polypropylene,polyvinylchloride, various fluoropolymers (for instance: PTFE, FEP,vinylidene fluoride, mixtures, alloys, copolymers, block copolymers,etc.), polysulfones or the like. Blends, alloys, mixtures, copolymers,block copolymers, of these materials are also suitable, if desired.

If a more flexible section is required, the outer tubing member (206)may be a polyurethane, low density polyethylene (LDPE),polyvinylchloride, THV, etc. and other polymers of suitable softness ormodulus of elasticity.

Although it is quite difficult to accomplish, the inventive catheterdesign allows the use in the distal portion of the catheter, thin-walledtubing of inherently more slippery polymers, such as PTFE and FEP andtheir mixtures, which have the benefit of being lubricious but otherwisewould have been used in a somewhat greater thickness. Production of agood adhesive joint between the helically wound ribbon (202) and theadhesive (204) is not an easy task. Clearly, greater thickness tubing ofthese polymers results in the resulting catheter section being somewhatstiffer. The wall thickness of the outer tubing member (206) may be asthin as 0.5 mil and as thick as 10 mil, depending upon catheter usage,portion of the catheter chosen, polymer choice, and the style ofcatheter.

Typically, the wall thickness of the tubing member will be between 0.5and 3.0 mils. This dimension is obviously only a range and each cathetervariation must be carefully designed for the specific purpose to whichit is placed.

Preferred combinations of polymers for catheter configurations will alsobe discussed below. It should also be noted at this point that each ofthe polymers discussed herein may be used in conjunction with radiopaquematerial such as barium sulfate, bismuth trioxide, bismuth carbonate,powdered tungsten, powdered tantalum, or the like so that the locationof the various pieces of tubing may be radiographically visualizedwithin the vessel.

The spiral wound ribbon (202) shown in FIG. 2 may also be of a varietyof different materials. Although metallic ribbons are preferred becauseof their strength-to-weight ratios, fibrous materials (both syntheticand natural) may also be used. Preferred, because of cost, strength, andready availability are stainless steels (SS308, SS304, SS318, etc.) andtungsten alloys. In certain applications, particularly smaller diametercatheter sections, more malleable metals and alloys, e.g., gold,platinum, palladium, rhodium, etc. may be used. A platinum alloy with afew percent of tungsten is preferred partially because of itsradiopacity.

The class of alloys known as super-elastic alloys is also a desirableselection. Preferred super-elastic alloys include the class oftitanium/nickel materials known as nitinol--alloys discovered by theU.S. Navy Ordnance Laboratory. These materials are discussed at lengthin U.S. Pat. Nos. 3,174,851 to Buehler et al., 3,351,463 to Rozner etal., and 3,753,700 to Harrison et al. These alloys are not readilycommercially available in the small ribbons required by the inventiondescribed here, but for very high performance catheters are excellentchoices.

When using a superelastic alloy, an additional step is usually necessaryto preserve the helical shape of the stiffening member. I have purchasednitinol wire and rolled it into a 1×4 mil ribbon. The ribbon is thenhelically wound onto a mandrel, usually metallic, of an appropriatesize. The winding is then heated to a temperature of 650°-750° F. for afew minutes, presumably annealing the ribbon. The helical coil thenretains its shape.

Metallic ribbons (202) that are suitable for use in this invention aredesirably between 0.5 mil and 1.5 mil in thickness and 2.5 mil and 8.0mil in width. By the term "ribbon", I intend to include elongatedshapes, the cross-section of which are not square or round and maytypically be rectangular, oval or semi-oval. They should have an aspectratio of at least 0.5 (thickness/width). In any event, for superelasticalloys, particularly nitinol, the thickness and width may be somewhatfiner, e.g., down to 0.30 mil and 1.0 mil, respectively. Currentlyavailable stainless steel ribbons include sizes of 1 mil×3 mil, 2 mil×6mil, and 2 mil×8 mil.

Suitable non-metallic ribbons include high performance materials such asthose made of polyaramids (e.g., KEVLAR) and carbon fibers.

It should be observed that the preferred manner of using non-metallicribbons in this invention is typically in combination with metallicribbons to allow "tuning" of the stiffness of the resulting composite.

Finally, in FIG. 2 may be seen an outer layer (208) of-a lubriciousmaterial such as a silicone or other, perhaps hydrophilic, material suchas a polyvinylpyrrolidone composition. These compositions are well knownand do not form a critical portion of the invention.

Typical of the catheter made using this invention are those in the 3French to 5 French range. The inner diameter of such catheters is then20 mils to 42 mils. However, I have made micro-catheters (discussed inmore detail below) having outside diameters of 18 mils to 34 mils. Theinner diameter of those catheters was 11 mils to 20 mils. The inventionis not limited to such sizes, however.

FIG. 3 shows a variation of the inventive catheter (210) in which thecross-sections of the ribbons (212 & 214) are generally oval rather thanrectangular than as shown in FIG. 2. Either cross-section is acceptablebut the oval section has less of a tendency to bind with guidewirespassing through the lumen. Additionally, the FIG. 3 variation shows theuse of two ribbons (212 & 214) wound side-by-side so to form a singlelayer of ribbon inside the outer tubing cover (206). The dual ribbonsmay be of the same composition or of differing compositions. They may beof the same size or of differing sizes. The number of ribbons may be ofany convenient configuration so long as the specific stiffness andkink-resisting criteria are met.

FIG. 4 shows another variation in which catheter sections made accordingto this invention are used in axial conjunction. Section (220) isgenerally as described in FIGS. 3 and 4 above, but section (222) is moreproximal and enjoys two outer covering layers (224) and (226). Covering(224) is simply a proximal extension of the polymeric covering insection (220); polymeric covering (226) is placed directly on the outersurface of the helically-wound coil (228). As has been noted elsewhere,coil (228) may be the same as or different than the coil found in themore distal section (220). Other methods for changing the stiffness ofvarious sections of a catheter made using sections of the inventivecatheter section are shown in FIGS. 5, 6, and 7. For instance, FIG. 5shows a distal section (230) having a helically-wound ribbon (232), anouter polymeric covering (234), and a radiopaque band (236). In thisvariation, the ribbon (232) is wound in such a fashion that adjacentturns are not contiguous. This allows the distal catheter section (230)to be quite flexible and kink-resistant. The intermediate section (238)retains the same outer covering (234), but the pitch of the coil hasbeen narrowed so that the flexibility of the midsection (238) is not ashigh as was the distal section (230).

The most proximal section (240) has no helically-wound ribbon at all,but instead uses a variety of polymeric or other tubing materials toform the stiffest portion of the catheter assembly. In this instance,the outer layer remains as found in the most distal section (230) andthe midsection (238). The inner layer in this instance is-a stiffermaterial, such as polyimide, polypropylene, or a stainless steel tube,known as a "hypotube".

FIG. 6 shows still another variation of forming the distal section of acatheter assembly which is flexible and yet provides a greater stiffnessfor other sections of the catheter assembly. For instance, in FIG. 6,the intermediate section (242) utilizes double layers of polymericmaterial, e.g., the outer tubing (234) (discussed above) on the outersurface and an inner tubing of similar or stiffer material (244) incontiguous relationship along the length of the section (242). The mostproximal section (246) shows only a short overlap between stiff distaltube (248) (perhaps made of the polyimide, polypropylene, nylon, orhypotube materials discussed above) and the outer layer (234). This is asimple arrangement and may be used, for instance, where cost is at apremium.

FIG. 7 shows still a further variation in which the most distal sectionis a composite of polymeric layers (252) and a braid (254). Thecomposition of the mid and proximal sections are not critical to theinvention. They may be of one type or the other depending upon therequirements of the particular application. The most significant ofbenefits is accrued when, however, the distal section is of the typespecified herein. Nevertheless, a variation shown in FIG. 8 depicts aninstance in which the non-kinking criteria of this invention is appliedin a mid-section. Catheter (256) uses a distal section having onlytubing (260) extending distally of the mid-section (262). Mid-section(262) comprises both outer tubing (260) and helically-wound ribbon (264)easily held in place according to this invention. Proximal section (266)is made stiffer by incorporating multiple layers of tubing, as discussedabove.

Although the exemplified catheter assemblies in FIGS. 1, 5, 6, 7, and 8each utilize three sections, it should be understood that this inventionis not so limited. The number of sections is selected by the designerwhen conceptualizing a specific use for a chosen device. Often, theoptimum number of sections ends up being three simply because of thephysiology of the human body, however, three or more may be involved inthis invention. The sections additionally need not be of constantstiffness. They may also vary in stiffness--typically as the distal endof a section is approached, the section becomes more flexible.

As was noted above, I have found that use of this method of constructionallows use of significantly smaller diameter catheters which stillremain kink-free and yet are quite useable. For instance, FIG. 9 shows ashort cross-section of a distal end of a vascular catheter (270) inwhich the outer section comprises an outer cover (206) and ahelically-wound ribbon (204) generally as shown in FIG. 2. Within thelumen defined by a helically-wound coil (204) may be found yet a smallercatheter device covering (272) and a helically-wound coil (274). Again,it is desireable that helically-wound coil (274) and covering (272) beadhesively attached to each other to lessen the chance of any kinkingtaking place. Within the lumen of the inner catheter is a guidewire(276) which, just as an inner catheter (275), is slidable within outercatheter (270), is slidable within the inner catheter (275). Forinstance, a guidewire (276) may have an outside diameter of 5 to 7 milsin this distal region and the outer diameter of inner catheter (275) mayhave an outer diameter of 12 1/2 to 14 mils.

As was noted above, the most distal portion of the distal section ofthis catheter (and preferably other sections as well) have a criticalbend diameter of no more than 3.5 mm, preferably no more than 2.5 mm,more preferably no more than 1.5 mm, and most preferably no more than1.0 mm. To some extent, the critical band diameter is also dependentupon the diameter of the catheter section and its components. Forinstance, I have made 3 French catheter section of the type shown inFIG. 2 (of stainless steel ribbon) with critical bond diameters lessthan 2.5 mm. Similarly, I have made catheter sections such as the innercatheter (275) shown in FIG. 9 with an outer diameter of 0.018" (ofplatinum-tungsten alloy ribbon) with band diameters less than 1.0 mm.

The test we utilize for critical bend diameter determination uses a testshown schematically in FIGS. 10A and 10B.

In general, as shown in FIG. 10A, a catheter section (300) is placedbetween two plates (desirably of plastic or glass or the like forvisibility) and often with an optional peg (302) to hold the cathetersection (300) loop in place. The ends of the catheter are then pulleduntil a kink appears in the body of the catheter. Alternatively, theratio of the outer diameters (major diameter:minor diameter) as measuredat apex (304) reaches a value of 1.5. FIG. 10B shows the cross sectionof the catheter sector at (304) and further shows the manner in whichthe major diameter and the minor diameter are measured. These twomethods provide comparable results although the latter method is morerepeatable.

Many times herein, we refer to the "region" section of the catheter.Where the context permits, by "region" we mean within 15% of the pointspecified. For instance, "the distal region of the distal section" wouldrefer to the most distal 15% in length of the distal section.

This invention has been described and specific examples of the inventionhave portrayed. The use of those specifics is not intended to limit theinvention in any way. Additionally, to the extent that there arevariations of the invention which are within the spirit of thedisclosure and yet are equivalent to the inventions found in the claims,it is our intent that this patent cover those variations as well.

I claim as my invention:
 1. A single lumen over-the-wire cathetersection comprising:an elongate tubular member having a proximal end anda distal end and a single passageway defining an inner lumen extendingbetween those ends, comprisinga.) a first ribbon stiffener having awidth and thickness, and said first ribbon stiffener is spirally woundto form axially-spaced-apart helical turns with a handedness to formsaid passageway and an outer stiffener surface and wherein said outerstiffener surface is at least partially coated with an adhesivematerial, and b.) at least one tubing member exterior to and contiguouswith and adherent to said first ribbon stiffener via said adhesivematerial wherein said exterior tubing member adherent to said firstribbon stiffener substantially prevents kinking at the at least onetubing member.
 2. The catheter section of claim 1 wherein the cathetersection has a critical bend diameter of no more than 3.5 mm.
 3. Thecatheter section of claim 1 wherein the first ribbon stiffener ismetallic.
 4. The catheter section of claim 3 wherein the first ribbonstiffener is a super-elastic alloy.
 5. The catheter section of claim 3wherein the first ribbon stiffener is nitinol.
 6. The catheter sectionof claim 3 wherein the first ribbon stiffener is stainless steel.
 7. Thecatheter section of claim 3 wherein the first ribbon stiffener is aplatinum-tungsten alloy.
 8. The catheter section of claim 1 wherein thetubing member is radiation sterilizable without substantial degradationof its physical attributes.
 9. The catheter section of claim 1additionally comprising at least a second ribbon stiffener of the samehandedness coaxially wound between the spiral turns of the first ribbonstiffener.
 10. The catheter section of claim 9 where the second ribbonstiffener comprises a ribbon having a thickness between 0.75 mil and 2.5mils and a width between 2.5 and 8.0 mils.
 11. The catheter section ofclaim 1 where the elongate tubular member has at least one region ofvariable stiffness between the proximal end and the distal end.
 12. Thecatheter section of claim 1 where the first ribbon stiffener has a pitchwhich varies between the proximal end and distal end.
 13. The cathetersection of claim 1 where the first ribbon stiffener comprises a ribbonhaving a thickness between 0.5 mil and 2.5 mil and a width between 2.5and 8.0 mil.
 14. The catheter section of claim 1 wherein the tubingmember comprises a polymer.
 15. The catheter section of claim 14 whereinthe tubing member comprises a polymer which can be heat-shrunk onto saidfirst ribbon stiffener.
 16. The catheter section of claim 15 wherein thetubing member comprises a polymer selected from polyethylene,ethylvinylacetate, polyethylene terephalate, polvinylchloride, and theirmixtures and copolymers.
 17. The catheter section of claim 16 whereinthe tubing member comprises EVA.
 18. The catheter section of claim 15wherein the adhesive material has a softening temperature higher thanthe heat shrink temperature of the tubing member but lower than themelting temperature of the tubing member.
 19. The catheter section ofclaim 1 wherein the adhesive material has been placed on an interiorsurface of the tubing member.
 20. The catheter section of claim 1wherein the adhesive material is exuded in situ from the tubing memberduring assembly of the catheter section.
 21. The catheter section ofclaim 1 wherein the adhesive material has been placed at least on theexterior surface of the wound first ribbon stiffener.
 22. The cathetersection of claim 1 wherein the adhesive material is selected frompolyimides and polyesters.
 23. The catheter section of claim 22 whereinthe adhesive material is a polyester.
 24. The catheter of claim 1 wherethe tubing member is radiopaque.
 25. The catheter of claim 1 whereinadjacent turns in the first ribbon stiffener are contiguous.
 26. Thecatheter section of claim 1 further comprising a second cover exteriorto the tubing member.
 27. The catheter section of claim 26 where thesecond cover comprises a material selected from polyimide, polyamides,polyethylene, polypropylene, polyvinylchloride, polyurethane,fluoropolymers including PTFE, FEP, vinylidene fluoride, and theirmixtures, alloys, copolymers, and block copolymers, polysulfones or thelike.
 28. The catheter section of claim 1 further comprising aremovable, slidable guidewire placed interior to and in slidablerelationship to said section.
 29. The catheter section of claim 1further comprising an interior catheter removably, slidably, andtelescopically placed interior to and in slidable relationship to saidsection.
 30. The catheter section of claim 29 further comprising aguidewire placed interior to and in slidable position to said interiorcatheter.
 31. A single lumen over-the-wire catheter comprising:anelongate tubular member having a proximal end and a distal end and asingle passageway defining an inner lumen extending between those ends,said elongate tubular member having:a.) a relatively stiff proximalsegment, and b.) a relatively flexible distal segment, said distalsegment comprisingi.) a first ribbon stiffener having a width andthickness, and said first ribbon stiffener is spirally wound to formaxially-spaced-apart helical turns with a handedness to form saidpassageway and an outer stiffener surface and wherein said outerstiffener surface is at least partially coated with an adhesivematerial, and ii.) at least one tubing member exterior to and contiguouswith and adherent to said first ribbon stiffener via said adhesivematerial wherein said exterior tubing member adherent to said firstribbon stiffener substantially prevents kinking at the at least onetubing member.
 32. The catheter of claim 31 wherein the distal segmentsection has a critical bend diameter of no more than 3.5 mm.
 33. Thecatheter of claim 31 where the proximal segment is composed of a secondcover comprising a proximal cover material, said second cover exteriorto a proximal extension of the tubing member and said first ribbonstiffener.
 34. The catheter of claim 31 further comprising at least oneintermediate segment having a flexibility intermediate the flexibilityof the distal and proximal segments, said intermediate segment defininga passageway between the relatively stiff proximal segment and therelatively flexible distal segment.
 35. The catheter of claim 34 whereinthe at least one intermediate segment is composed of an extension of thetubing member and said first ribbon stiffener.
 36. The catheter of claim34 where the intermediate section-of the catheter additionally comprisesa second ribbon stiffener of the same handedness coaxially wound betweenthe spiral turns of the first ribbon stiffener.
 37. The catheter ofclaim 34 where the proximal section of the catheter comprises a metallichypotube.
 38. The catheter of claim 34 where the proximal section of thecatheter comprises a polymeric tube proximally abutting the tubingmember and said first ribbon stiffener.
 39. The catheter of claim 31where the proximal section of the catheter additionally comprises asecond ribbon stiffener of the same handedness coaxially wound betweenthe spiral turns of the first ribbon stiffener.